1. Field of the Invention
The present invention relates generally to image forming devices, and particularly to scanners and scanning methods. More specifically, the present invention discloses a linear light diffusing structure to form a substantially uniform light output beam for illuminating a media sheet when placed on an imaging surface.
2. Description of the Related Art
Scanners are used to scan an image from a sheet of media and create scanned image data which can be displayed on a computer monitor, printed, sent via facsimile transmission, etc. Scanned image data may be saved in memory or a magnetic or optical drive, or other memory device. Scanning devices may be packaged in a stand-alone housing or as a part of a multi-functional product, including a product having a printing component, to perform scanning as well as standard copying functions.
In a conventional scanner, the desire to use light emitting diodes (LEDs) as a light source for scanner is not new. LEDs are mercury free, instant-on and compact. However there are a few factors that hinder the use of LEDs in a high speed document scanner. The top hindering factors are cost and output intensity. With the rapid advancement in research, development and manufacturing of LEDs, cost and output performance are reaching acceptable levels and therefore there is the renewed interest in using high powered LEDs as the illumination source for high speed documents scanners. In addition to cost and output level, there are additional factors that often need to be carefully controlled. One is thermal stability. The inherent nature of a small LED chip outputting a high intensity light presents challenges to dissipate heat efficiently so that the LED is not thermally affected both in output intensity and spectral composition to negatively impact scan image quality. Another factor is the non-uniformity of the light profile when a limited number of LEDs are used to save cost. Since the LED's light emitting PN junction is usually small, the light output profile can be highly irregular and difficult to control even with elaborate lens designs which disadvantageously increases cost.
Given the foregoing, it would be desirable therefore to provide a substantially thermally stable, light generating structure which provides a substantially uniform light output for a scanning device.